Structuring incoming environmental and efficiency standards for heavy-duty vehicles so that they are based on the full vehicle including the engine as well as having separate standards for just the engine, could result in better standards, according to research by the American Council for an Energy Efficient Economy.

But after comparing the standards in relation to: the promotion of advanced technologies; the ability of them to reflect real-world performance; comparability with criteria emissions testing; practicable compliance and enforcement; compliance flexibility; and low-cost testing, the ACEEE found that the approach of combining full-vehicle standards with additional standards that just target engines (called option D in the ACEEE study) fared better than assessing just the vehicle (option B) as a whole or just the engine (option A).

When compared to the “promotion of advance technologies” criterion the paper found that option D provided the advantages of options A and B, while avoiding their disadvantages. By comparison, the engine only option would fail to advance transmissions, hybrids, or integrating technologies, according to the study. The full vehicle option would render it “difficult” to ensure progress on the engine or other components not produced by the truck manufacturer, ACEEE says.

According to ACEEE, the primary purpose of the standards is to drive efficiency technologies for heavy-duty vehicles, and option D’s superior performance on that criterion must be given extra weight. Option D also did as well as any other option in its ability to reflect real-world performance, another key criterion, the nonprofit says.